Search Results (1,730)

Interest in isolated electrical systems powered by renewable energy has driven the development of alternatives to traditional Wind–Diesel Systems (WDS) due to their unwanted emissions and regulatory constraints. In this context, clean and efficient hybrid architectures are needed to comply with regulations and ensure stable operation under variations in user load and wind generation. This paper proposes an integrated isolated hybrid system consisting of a fuel cell replacing the Diesel Generator (DG). To fulfil the role of the synchronous generator in the diesel-group, the fuel cell operates under a Grid-Forming (GFM) control scheme, acting as a virtual synchronous machine that establishes the system’s voltage and frequency. The main aim of the hybrid system is for the wind turbine to supply most of the active power to the loads, thereby minimising hydrogen consumption. A key challenge in these systems is maintaining power balance, particularly preventing reverse flows in the fuel cell system, which has less margin than the diesel generator. In this paper, a Dump Load (DL) quickly dissipates excess power and prevents reverse power conditions. Overall, the proposed system eliminates the need for diesel generation, thereby eliminating emissions while maintaining operational stability. Simulation results demonstrate the correct functioning of the system in the presence of significant variations in load and wind power generation. Full article

To address global carbon reduction demands, oxy-fuel combustion in circulating fluidized beds (oxy-CFB) has emerged as a highly promising carbon capture technology, offering extensive fuel flexibility and facilitating bioenergy with carbon capture and storage (BECCS). However, its commercialization is hindered by significant energy penalties and complex scale-up challenges. This review comprehensively analyzes the fundamental multiphase mechanisms, heat transfer behaviors, and multi-pollutant emission characteristics of oxy-CFB systems, drawing upon multiscale modeling advancements and operational data from pilot to 30 MW_th industrial demonstrations. Replacing air with an O₂/CO₂/H₂O mixture fundamentally alters gas–solid hydrodynamics and char conversion pathways, necessitating active fluidization state re-specification. Despite shifting optimal desulfurization temperatures and introducing recarbonation risks, the technology demonstrates inherent advantages in synergistic pollutant control, including the complete elimination of thermal NO_x. While atmospheric oxy-CFB is technically viable, transitioning to pressurized operation is critical to minimizing system efficiency penalties. Furthermore, integrating oxygen carrier-aided combustion (OCAC) and developing advanced predictive control strategies are essential to managing multi-module thermal inertia and enabling rapid dynamic responsiveness for modern power grids. Full article

This study addresses the decarbonisation of the glass industry from an integrated energy system perspective, analysing the role of renewable electricity, furnace electrification, and hydrogen in meeting the high and continuous thermal demands of glass melting. While direct electrification represents the most energy-efficient option, its implementation is challenged by the intermittent nature and limited operating hours of renewable generation, scale constraints, and technological limitations in replacing fossil-based processes, highlighting a potential complementary role for hydrogen. A general methodological framework is first developed and then applied to a representative oxyfuel glass furnace using mixed-integer linear programming (MILP) optimisation that minimises melting costs while accounting for variable solar and wind generation, battery storage, and hydrogen production and storage. The results show that high levels of furnace electrification combined with wind-dominated renewable supply yield the lowest decarbonisation costs, which can become negative at moderate decarbonisation levels. Under the current solar–wind capacity expansion mix, the integration of battery and hydrogen storage extends achievable emission reductions from around 50% to 80%, with hydrogen acting as a complementary solution to electrification. Sensitivity analysis of energy and carbon prices, as well as technology investment costs, identifies the economic conditions in which storage-based solutions become cost-effective, highlighting the strategic role of hydrogen under conditions of low electricity prices and high fuel prices. The findings demonstrate viable pathways for deep decarbonisation of the glass sector and provide a transferable methodological framework for optimal renewable energy integration in other hard-to-abate industrial sectors facing similar constraints. Full article

As a critical actuator in aero-engine control systems, the health condition of the Fuel Metering Unit (FMU) directly influences flight safety and maintenance efficiency, making the precise prediction of its degradation process a core task in the engine’s Prognostic and Health Management (PHM). This paper presents a novel inverted stabilized LSTM-Transformer (isLTransformer) approach for predicting the health state of aero-engine FMUs, addressing the limitations of existing methods in modeling long-sequence multivariate data. Firstly, a Composite Health Indicator (CHI) is constructed through semi-supervised learning (SSL), which fuses multi-sensor monitoring data to quantitatively characterize the degradation trend of the FMU throughout its operational lifecycle. Secondly, the proposed isLTransformer model is designed by replacing the feedforward network in traditional iTransformer with a stabilized LSTM module, which maintains the self-attention mechanism’s capability to explicitly model dynamic correlations between multiple variables while enhancing the ability to capture nonlinear degradation within individual variables. A physical FMU test bench is designed for the real-world PHM degradation experiments, and the collected dataset was used to demonstrate the effectiveness of the proposed method. Evaluation metrics, including Root Mean Square Error (RMSE) and Mean Absolute Error (MAE), are employed to assess the prediction accuracy. The proposed method demonstrates high monotonicity and trend consistency in CHI construction. Compared to the inverted Transformer (iTransformer) and iTransformer- Bi-directional Long Short-Term Memory (BiLSTM), the proposed isLTransformer framework demonstrates significantly reduced prediction errors, validating its superiority in multivariate long-sequence prediction tasks and effectiveness for aero-engine FMU health prediction. Full article

Dual-fuel combustion is often proposed for diesel engines as a means to partially replace conventional diesel with cleaner and/or more sustainable alternatives, such as those derived from green hydrogen. However, the low reactivity of these fuels (i.e., methane, hydrogen, and ammonia) often leads to prolonged ignition delay (ID) and combustion instability. This challenge could potentially be overcome using nanomaterials, which are additives that could improve reactivity and compensate for autoignition deficiencies. Thus, this study evaluates the effect of carbon nanotubes (CNTs) dispersed in diesel fuel on the autoignition process under dual-fuel operation. CNTs were dispersed at a concentration of 100 mg/L and stabilized with surfactant sodium dodecylbenzene sulfonate (SDBS). The resulting nanofuels were then tested in a constant volume combustion chamber (CVCC) using methane, hydrogen, and ammonia as secondary fuels across various energy substitution ratios and temperatures (535 °C, 590 °C and 650 °C). The results show that the impact of CNTs on ID is negligible, especially at high temperatures. At the lowest tested temperature (535 °C) and 40% methane substitution ratio, only slight reductions in ID were obtained. Nevertheless, this effect is less significant at higher temperatures (590 °C and 650 °C). Regarding pressure gradient, the addition of CNTs and SDBS generally induced a decrease in pressure-peak of up to 15%. This trend is attributed to the trapping of fuel droplets within the CNT structures, which creates a physical barrier that delays vaporization. Results confirm that autoignition, which is expected to be the main phenomenon influenced by CNT addition, is not enhanced. Full article

The use of resource-saving technology in road construction material production is a current problem, the solution of which will allow us to increase the environmental and economic efficiency of the road construction industry. Nowadays, secondary raw materials are widely used in highway construction, obtained both from the waste of old road construction materials and collected from other industries. During asphalt production, up to 90% of raw materials can be replaced by reclaimed asphalt pavement (RAP). This technology requires residual binder modification to reduce the negative impact on the technological and operational asphalt concrete properties. On the other hand, the use of rubber crumbs or granules obtained from the disposal of old car tires in asphalt–concrete mixtures is widespread. However, some types of car tires cannot be used as raw materials to produce an effective modifier. Truck tires and tires from special vehicles are suitable for use as a modifier for asphalt–concrete mixtures. Tires designed for passenger cars do not contain enough polymer. As an experiment on asphalt–concrete mixture production using secondary resources only, a testing facility was developed. The testing facility uses hot gas obtained by burning automobile tires in a special oven as a heat source. Rubber residues from the recycling of automobile tires are used as fuel, which cannot be used to produce rubber powder or granules. RAP obtained by cold milling of the pavements of city and public roads was used as the object of the research. When studying the characteristics of the asphalt–concrete-mixture-based binder, it was found that the sulfur compounds present in the composition of hot gases change the properties of the binder, leading to a serious deterioration in the technological characteristics of asphalt–concrete mixtures. The asphalt–concrete mixture obtained during RAP processing is characterized by a narrow temperature range in which it can be laid and compacted to the required density values. After laying the pavement, quality control revealed a significant variation (the number of air voids ranged from 0.8 to 5.5%) in the average density of samples taken from the compacted layer. In addition, there were significant violations of the longitudinal evenness of the finished coating. Experiments were carried out to extract the binder from asphalt–concrete mixtures before and after regeneration. The physico-mechanical and rheological characteristics were studied and qualitative analysis of the binder was realized by IR spectroscopy. The data obtained allow us to establish the mechanism of how sulfur-containing gases influence the bitumen binder’s properties in asphalt mixtures. Additionally, the features of thermo-oxidative degradation occurring during the hot recycling of asphalt–concrete mixtures were established. A justification is also given for the need to use anti-aging modifiers to restore the properties of the residual binder. Full article

This study investigates the fuel discrimination capability of the flame volume mixing method (FV mixing method) in predicting the lean blowout (LBO) limits of different fuels. Conventional FV-based models exhibit limited sensitivity to variations in fuel properties, especially under lean conditions and for sustainable aviation fuels. In this work, an improved FV mixing method is proposed by replacing the classical droplet evaporation treatment with the Abramzon–Sirignano droplet evaporation model, which accounts for fuel-dependent liquid properties, Stefan flow, and coupled convective heat and mass transfer between the gas phase and droplets. As a result, the proposed method shows enhanced sensitivity to fuel variability and improves the prediction accuracy of the LBO limit for the sustainable aviation fuel Cat-C1. The model performance is validated through numerical simulations and compared with experimental data. The results indicate that, compared with the baseline FV mixing method, the proposed approach reduces the LBO prediction error by 5.7%. The improved FV mixing method provides a more robust framework for LBO prediction, with potential applications in fuel characterization and combustion optimization. Full article

Bio-CO₂ is part of the natural carbon cycle and represents a sustainable carbon source for the production of Renewable Fuels of Non-Biological Origin (RFNBOs), such as synthetic methanol. This study addresses the critical knowledge gap in aligning diverse biogenic CO₂ sources with e-methanol requirements in the EU by providing harmonized mapping, based on datasets, literature sources, and reported industrial statistics at the sectoral and country level. Bio-CO₂ streams from biogas and biogas upgrading, biomass combustion, pulp and paper, bioethanol production, and the food and beverage sector are evaluated for total emissions, CO₂ concentrations and purity, the geographical distribution, seasonality, and impurity profiles. Results show that approximately 350 Mtpa of bio-CO₂ are emitted across the EU, with highly heterogeneous characteristics. Biogas upgrading and fermentation-based processes generate highly pure CO₂ streams (>98–99%), yet their small and dispersed nature complicates logistics. In contrast, biomass-combustion and pulp and paper sectors provide large volumes (around 214.6–298.2 Mtpa and 73.9 Mtpa CO₂, respectively), but in diluted streams (typically 3–15% and 10–20%). Replacing just 10% of the EU maritime fuel demand with e-methanol would require 53.6 Mtpa of bio-CO₂ and 58 GW of electrolyzer capacity, a stark contrast to the current operational 385 MW. The findings highlight the need for infrastructure planning and aggregation hubs to enable the large-scale deployment of RFNBO methanol in the maritime sector. Full article

Currently, hydrogen is considered a primary option for replacing fossil fuels across various processes, which can reduce greenhouse gas emissions and mitigate global warming. To achieve these goals, hydrogen should be produced using non-polluting processes, such as water electrolysis powered by renewable energy sources. This method requires feeding the converter with an unregulated voltage source. A quadratic step-down converter can be connected between a DC source and a Proton Exchange Membrane (PEM) electrolyzer to produce hydrogen. To mitigate variations in the generated output voltage and intermittent power supply to a PEM electrolyzer, a DC-DC converter is used as an interface. A converter model can be combined with a static or dynamic model of the PEM electrolyzer to yield switched models and, after averaging, linear state-space models. These models can be used to design robust controllers for green hydrogen production, thus significantly reducing greenhouse gas emissions. This work presents experimental and simulation results. Full article

The accelerated decarbonization agenda of the European Union, supported by the European Green Deal, the Fit for 55 package, and REPowerEU, increases pressure on member states to reduce dependence on fossil fuels and expand renewable generation. Poland, whose power sector remains strongly coal-dependent, faces one of the most challenging and capital-intensive transition pathways in the EU. This study provides a comprehensive assessment of the costs and economic viability of Poland’s energy transition, focusing on the feasibility of replacing coal-based electricity generation with renewable technologies. The analysis applies three financial evaluation methods: net present value (NPV), internal rate of return (IRR), and levelized cost of electricity (LCOE). These tools are used to estimate investment costs of selected renewable technologies, assess the potential for coal substitution in the energy mix, and determine the profitability of renewable projects under selected scenarios. The results show that onshore wind power demonstrates the most favorable investment parameters, including the lowest LCOE and the shortest payback period, while photovoltaics exhibit lower profitability in the analyzed conditions. Nuclear energy may serve as a complementary stable source to variable renewables. The findings provide evidence-based insights supporting national energy planning and the design of future policy instruments. Full article

With the aim of reducing greenhouse gas emissions from energy consumption and advancing the green energy transition, this study employs sodium hydroxide and water glass as activators to facilitate the replacement of fossil fuels with renewable energy sources, with physically activated recycled micro-powder serving as an auxiliary cementitious material to prepare alkali-activated recycled hollow concrete. This study pioneers the application of the coarse aggregate tight-packing theory (bulk density method) to the preparation of alkali-activated recycled hollow concrete containing sand. By integrating Matlab image binarization techniques, we quantitatively analyzed the causes of porosity deviation, achieving precise alignment between target and actual porosity. This work fills a theoretical gap in the quantitative design of porosity for this concrete type. Additionally, the effects of different binder material dosages and pore volumes on the mechanical properties and permeability coefficients of sand-containing porous concrete were evaluated. Experimental results indicate that the calculated pore volume of sand-containing porous concrete prepared using the dense-packing theory (bulk density method) exhibits a smaller average error compared to the actual pore volume. As the amount of cementitious materials increases, the compression strength of permeable concrete gradually increases. When the cementitious material content is 450 kg/m³, and the target porosity is 15%, the concrete’s 28-day compressive strength reaches 21.4 MPa. At a porosity of 15%, the permeability coefficient ranges from 5.2 to 5.7 mm/s. Full article

The sintering process represents a primary source of dust, SO₂, NOx, and CO₂ emissions in steel mills. Utilizing high-grade concentrate with low impurity content can directly reduce slag generation at the source, thereby decreasing fuel consumption and minimizing associated emissions. This study investigated the physicochemical properties, microstructure, and elemental distribution of hematite concentrates (H2 and H3) and H1 sinter fines. Sinter pot tests were conducted to evaluate the effects of blending these two concentrates on sintering performance and key quality indices. Microstructural analysis and quantitative phase composition statistics of the sintered products were performed to elucidate the mechanisms by which these concentrates influence sintering outcomes. Results demonstrated that replacing 33% H1 sinter fines with 33% H2 or H3 concentrates reduced the tumbler index from 73.6% to 68.5% and 73.2%, respectively. The productivity coefficient decreased to 68.5% and 73.2%, while solid fuel consumption increased from 73.9 kg/t to 90.5 kg/t and 81.2 kg/t. RI declined from 80.0% to 77.9% and 78.4%, whereas RDI improved from 72.9% to 76.8% and 75.8%. Full article

Riboflavin (RF; vitamin B₂) is an essential micronutrient with broad applications in the food, feed, pharmaceutical, and cosmetic industries and is increasingly relevant in bioelectrochemical systems and environmental biotechnology. Microbial fermentation has replaced chemical synthesis as the dominant industrial production route due to its superior sustainability and scalability. However, despite substantial progress, RF biosynthesis remains constrained by imbalances in precursor supply, complex redox regulation, and regulatory feedback mechanisms that limit metabolic flux toward guanosine triphosphate and ribulose-5-phosphate. This review provides an updated, integrative analysis of RF biotechnology, encompassing biosynthetic pathways, transcriptional and redox-regulation, strain improvement strategies, and fermentation process optimization. Representative industrial producers—including Bacillus subtilis, Ashbya gossypii, and Candida famata—are critically evaluated for productivity, yield, and metabolic robustness, with reported titers reaching up to 29 g L⁻¹ in engineered systems. Emerging microbial platforms, including lactic acid bacteria, thermotolerant and methylotrophic microorganisms, and electroactive bacteria, are discussed in the context of niche applications such as food biofortification and microbial fuel cells. Special emphasis is placed on oxidative stress as a regulatory signal influencing RF overproduction, metabolic rewiring strategies to alleviate precursor bottlenecks, and the biosynthesis of RF derivatives (FMN, FAD, roseoflavin, and 8-aminoriboflavin). In addition, biosafety, regulatory constraints, concerns about genome stability, and antibiotic-free engineering approaches are examined as critical determinants of future industrial competitiveness. By integrating molecular regulation, metabolic engineering, fermentation design, emerging applications, and regulatory perspectives within a unified framework, this review outlines current bottlenecks and future directions for developing safer, more robust, and economically competitive RF-producing microbial platforms. Full article

Bioethanol is an alternative energy source to fossil fuels and can serve as a raw material for the production of sustainable aviation fuel. Poly(3-hydroxybutyrate) (PHB) is a biodegradable plastic with the potential to replace petrochemical plastics. Lignocellulose has a renewable and eco-friendly nature, and it is a key factor in determining the environmental impact of bioethanol and PHB. In this study, we addressed this issue by developing Escherichia coli for the co-production of bioethanol and PHB from rice straw hydrolysate (RSH). Metabolic evolution was employed to enhance ethanol tolerance in the ethanologenic E. coli strain. To mitigate the toxicity of RSH, the strain was modified by rewiring the pentose phosphate pathway and subsequently subjected to metabolic evolution. The strain was further reshaped by reprogramming xylose metabolism and recruiting the PHB synthesis pathway. As a result, the engineered strain simultaneously utilized glucose and xylose while producing 19.8 g/L of bioethanol and 3.5 g/L of PHB in 30 h. The bioethanol yield and the PHB content account for 0.40 g/g and 38% of dry cell weight, respectively. Overall, it indicates the potential application of this developed strain in lignocellulosic biorefineries. Full article

Amid growing urgency for net-zero delivery and calls for simplified energy system modelling, this study presents a techno-economic framework, termed “End-state Decarbonisation Resource Analysis” (EDRA), for evaluating national decarbonisation strategies. EDRA integrates demand estimation, technology replacement, generation calculation and economic assessment, and employs scenario modelling and optimisation to estimates the technical, geographical, and financial resources required for full national decarbonisation. The framework offers a simplified yet comprehensive approach for national energy system assessment. Applied to the UK, EDRA reveals substantial gaps between current government capacity targets and the requirements of a fully decarbonised system aligned with the UK’s policy goals of net-zero, energy independence and energy security. Meeting these aims would require more than triple the nuclear target, over double the offshore wind target, more than 400 GW of electrolysers, combined cycle hydrogen turbines and electricity grid, ~50 thousand km² of land for wind and solar, and trillion-pound scale investment. Delivering this scale of resource deployment within 25 years presents a significant policy challenge. Nevertheless, the results demonstrate clear advantages of a decarbonised electrification system over fossil fuel-based alternatives. A key policy recommendation is to prioritise demand reduction to ease generation resource pressure. Full article